JPH07287815A - Nonmagnetic ceramics for recording and reproducing head and its production - Google Patents

Abstract

PURPOSE:To provide such a nonmagnetic ceramic material and its production in which deformation of the material during working is suppressed, the load during working is small, the working rate per unit time is large, surface unevenness after working is small, and the material shows small attaching force and frictional force with a disk and excellent in sliding property. CONSTITUTION:The ceramic material consists of 1-17vol.% titanium oxide and 99-83vol.% alumina, and it is preferable that 0.1-5 pts.wt. zirconia is added to 100 pts.wt. of the main component comprising 1-17vol.% titanium oxide and 99-83vol.% alumina. This nonmagnetic ceramic is obtd., for example, by mixing 1 17vol.% titanium oxide having <0.6mum average particle size and 99-83vol.% alumina as the source material, molding this mixture powder or sintering the mixture powder, and then subjecting the mixture powder or the molded or sintered body to hot pressing or hot hydrostatic pressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to non-magnetic ceramics for recording / reproducing heads used for ceramic substrates for thin film magnetic heads, sliders for various magnetic heads, spacers for magnetic heads, tape guides for magnetic recording, etc. It relates to the manufacturing method, the material itself has a large hardness,
Since it has a Young's modulus, it can manufacture a head with high processing accuracy, can provide an information recording device with excellent reliability, and can also provide a frictional force and an attractive force with respect to a recording medium and a recording tape, which are high-density recording media. The present invention relates to a non-magnetic ceramic for a recording / reproducing head having a small value and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, the densification of magnetic recording has made rapid progress. With this densification, high coercive force media such as hard disks, 8 mm VTRs, electronic still cameras, video floppy disks and digital audio systems have been developed. As a magnetic head for recording / reproducing, a thin film head suitable for increasing the density of magnetic recording using a magnetic thin film has been attracting attention, in place of a conventional magnetic head using ferrite or the like.

A thin film head using a magnetic thin film is manufactured, for example, as follows. First, a sputtered film of alumina is formed as an insulating film on the surface of a substrate having a diameter of 6 inches to 3 inches, and then thousands of transducers are formed on the upper surface of the alumina film by using a lithography technique. An insulating alumina film is formed again on the substrate on which the transducer is formed. Then, it is obtained by cutting out individual magnetic heads from the substrate in consideration of the polishing allowance as the slider. After the bar material including the individual thin film heads is cut out, one surface of the bar material is polished as a sliding surface.

By the way, in recent years, as the recording density of the Winchester type magnetic head has been improved, the flying height of the magnetic head from the disk surface has been reduced to submicron or less. The flying height of the slider changes due to the difference. In order to reduce this change in the flying height, not only the conventional positive pressure portion is provided on the air bearing surface, but also a minute groove (recess) is formed in a part of the sliding surface to form a negative pressure portion. It has been proposed to make the flying height of the head constant at the inner and outer circumferences.

Therefore, for the above reasons, after polishing the sliding surface which is one surface of the bar material cut out from the substrate,
Grooves (recesses) are formed on this sliding surface. This groove is generally machined, but when a negative pressure slider having a groove of several μm is formed, it is processed by ion beam milling, reactive ion milling, chemical etching or the like.

[0006]

In the conventional thin film head, the bar material for the slider is warped by a few microns per 50 mm in length during the above cutting process, and the magnetic gap depth (throat height) on the sliding surface is increased. Although the change in the value was about a few microns, the influence on the electric characteristics for reproduction and recording was small.

However, in a magnetic head for higher density recording, variations in the gap depth due to the warp cause deterioration of electrical characteristics. Therefore, the warp when the slider bar material is cut out needs to be submicron or less per 50 mm in length. Alumina / titanium carbide-based materials have been conventionally used as slider materials for magnetic heads for high-density recording, etc.
Although it is possible to reduce the warpage when the slider bar material is cut out to some extent, there is a problem that it is difficult to perform accurate cutting in a short time because the load when cutting with a diamond grindstone is large. It was

Further, when the groove is formed in the slider bar material, it is necessary to finely process the sliding surface by ion milling or the like, but from the viewpoint of mass production and accuracy, the processing time and the uniformity of the processed surface are required. Is an important property in manufacturing. However, the conventional alumina / titanium carbide composite material has a problem that the amount of processing per hour by ion milling is small and the unevenness of the processed surface after ion milling is large. That is, in recent years, a material having a high processing speed by ion milling and a small processing surface unevenness is required.

Further, the conventional thin-film head slider material made of alumina / titanium carbide has a large attraction force and frictional force with the disk, which causes failure of the head crush or the like, and significantly reduces the reliability of the information recording apparatus. There was a problem. In order to improve the reliability of the magnetic head, there has been a demand for a material having a small sliding force and a small frictional force or an attractive force generated between the magnetic head and the disk.

In order to reduce the frictional force and the suction force between the recording disk and the recording / reproducing head, it has been proposed to reduce the suction force by forming a crown or the like on the air bearing surface of the head. , The size of this crown is a few nanometers.
It is necessary to improve the accuracy of the device, which makes it difficult to mass-produce inexpensive heads.

The present invention can suppress the deformation of the grinding process by the diamond grindstone, etc., can perform the precision processing, the load at the time of the grinding process is small, and the processing amount per minute in the fine processing such as ion milling is large. It is an object of the present invention to provide a non-magnetic ceramic having a small unevenness, a small adsorbing force and a frictional force with a disk and excellent slidability, and a manufacturing method thereof.

[0012]

As a result of studying the above-mentioned problems, the present inventor found that in the non-magnetic material for head,
By increasing the Young's modulus of the material itself, the deformation of the slider bar material during processing can be suppressed, and the non-magnetic ceramics for the recording / reproducing head can contain titanium oxide of 1 to 17% by volume and alumina of 99% by volume. By including rutile crystal phase as titanium oxide, precision processing is possible, the grinding processing load is small, the processing speed by ion milling is high, the irregularities on the fine processing surface are small, and the disk The inventors have found that it is possible to obtain a material having a small frictional force with respect to and an attractive force and having excellent sliding characteristics, and have reached the present invention.

That is, the non-magnetic ceramic for a recording / reproducing head of the present invention comprises 1 to 17% by volume of titanium oxide and 99 to 83% by volume of alumina.
.About.17% by volume, 99 to 83% by volume of alumina, and preferably 100 parts by weight of the main component, and 0.1 to 5 parts by weight of zirconia. Such a non-magnetic ceramic for a recording / reproducing head is, for example,
Titanium oxide having an average particle size of the raw material of 0.6 μm or less is 1 to 1
It is obtained by hot pressing or hot isostatic pressing of a mixed powder containing 7% by volume and 99 to 83% by volume of alumina, or a molded body of the mixed powder or a sintered body of the mixed powder. Alternatively, for example, a mixed powder containing 1 to 17% by volume of titanium oxide and 99 to 83% by volume of alumina having a raw material having an average particle size of 0.6 μm or less, or a molded body of this mixed powder, or baking of the mixed powder. It is obtained by hot pressing or hot isostatic pressing of the bonded body, and then heat-treating at 800 to 1200 ° C. in an oxidizing atmosphere.

Here, the titanium oxide and the alumina are limited to the above ratios because the sliding characteristics and the sintering due to the titanium oxide are set when the titanium oxide is less than 1% by volume (the alumina is more than 99% by volume). If the titanium oxide exceeds 17% by volume (alumina is less than 83% by volume), the Young's modulus becomes small and the deformation during processing of the bar material becomes large. This is because it becomes difficult to accurately machine the air bearing surface of the slider into a flat surface. Also, the milling surface roughness tends to be high. Particularly, from the viewpoint of frictional force with a disc and adsorption force, which are sliding characteristics, it is desirable that titanium oxide is contained in an amount of 10 to 17% by volume and alumina is contained in an amount of 90 to 83% by volume. , Or from the viewpoint of accurately processing a flat sliding surface, titanium oxide is 3.6 to 10.1% by volume, and alumina is 96.4 to 8%.
It is desirable to contain 9.9% by volume.

The non-magnetic ceramic material of the present invention is
It is desirable that 0.1 to 5 parts by weight of zirconia is contained with respect to 100 parts by weight of the main component composed of titanium oxide and alumina, but this is because the addition of zirconia improves the chipping characteristics during machining, resulting in a flat surface. This is because a smooth sliding surface can be obtained. Here, the content of zirconia of 0.1 to 5 parts by weight with respect to the main component means that zirconia is less than 0.
If the amount is less than 1 part by weight, the edge portion produced by processing with a diamond wheel or groove processing is likely to be chipped, and if the amount is more than 5 parts by weight, the Young's modulus of the material tends to decrease, which is not preferable. Is. The amount of zirconia based on 100 parts by weight of the main component composed of titanium oxide and alumina is 3 to 5 parts by weight from the viewpoint of obtaining a flat sliding surface, and 0.1 to 3 parts by weight from the viewpoint of high Young's modulus. It is desirable to do.

The non-magnetic ceramic material of the present invention preferably has a volume resistivity of 10 ¹⁰ Ωcm or more, which is close to a conductive material when the volume resistivity is less than 10 ¹⁰ Ωcm. , Because the current leaks. Volume resistivity is 1 x from the point of view of insulating material
It is preferably 10 ¹¹ Ωcm or more, and more preferably 1 × 10 ¹² Ωcm or more from the viewpoint of preventing leakage current. In the non-magnetic ceramic of the present invention,
The average crystal grain size of titanium oxide in the sintered body is 1 μm.
The following is desirable. This is because the surface roughness of the finely processed surface of ion milling can be reduced. The average crystal grain size of titanium oxide is preferably 0.6 μm or less, and particularly preferably 0.3 μm or less.

Further, in the non-magnetic ceramics of the present invention, for example, the average particle size of the raw material is 0.6 μm or less (50% particle size by microtrack, where 50% particle size by microtrack is the particle size and integrated value). In the graph of the volume fraction, a mixed powder containing titanium oxide and alumina having a cumulative volume fraction of 50% is hot-pressed or hot isostatically treated (HIP), or the mixed powder is molded. It can be obtained by hot pressing or hot isostatic pressing of the body, or hot pressing or hot isostatic pressing of the sintered body obtained by molding and firing the mixed powder as described above. Among these, it is particularly preferable to subject the pre-sintered body produced in a vacuum firing furnace, an oxidizing atmosphere firing furnace, or the like to hot isostatic pressing.

The average particle size of the titanium oxide raw material is 0.6
The reason why the particle size is less than or equal to μm is that if it is greater than 0.6 μm, the sintering temperature becomes high, so that the grain size of the alumina crystal increases,
This is because pores remain in the sintered body and it becomes difficult to remove them. Further, even if the sintered body is densified, the surface roughness Ra of the processed surface finely processed by ion milling is 1
This is because it becomes as large as 00 nm or more and is not suitable as a slider material, for example. The raw material particle size of this titanium oxide is preferably 0.3 μm or less, and particularly preferably 0.2 μm or less.

The reason why hot pressing or hot isostatic treatment is adopted for firing is that pores of 1 μm or more in the sintered body can be removed. The hot press treatment is performed in a carbon mold at a pressure of 50 to 500 kgf / cm ² , 110.
It is carried out at 0 to 1300 ° C. for 0.5 to 1 hour, and the hot isostatic treatment is carried out at a pressure of 500 to 20 in an argon or nitrogen atmosphere.
It is suitable to carry out at 00 kgf / cm ² and 1000 to 1300 ° C. for 1 hour.

In the present invention, after hot pressing or hot isostatic pressing, 800 to 1 in an oxidizing atmosphere.
It is desirable to perform heat treatment at 200 ° C., because this is to increase the volume resistivity. Where 800-12
The reason why the heat treatment was performed at 00 ° C. is that if the temperature is 800 ° C. or less, the volume resistivity cannot be sufficiently increased.
This is because pores are generated when heat treatment is performed at a temperature higher than 200 ° C.

[0021]

When the air bearing surface of the slider is mirror-finished, it is necessary to strictly control the flatness of the air bearing surface facing the disk as the flying height decreases. FIG. 1 shows a schematic diagram in which the deformation amount of a work in a state where a load is applied to the work during mirror finishing is calculated by the finite element method. In such a state, when the work fixing jig is fixed with, for example, an adhesive, the force of f acts on the end portion due to the effect of the adhesive. still,
The work shape is 4 mm × 1.3 mm × 2.5 mm,
The load was 1.0 kgf. And Young's modulus is 130
00 kgf / mm ² , 25000 kgf / mm ² , 40
As a result of calculation for each material different from 000 kgf / mm ² , the work deformation amount Δx is 2.19 × 10 ⁻⁴ ,
It is 1.14 × 10 ⁻⁴ and 7.13 × 10 ⁻⁵ , and it can be seen that the larger the Young's modulus, the smaller the deformation. From this, it is understood that a material having a larger Young's modulus can be processed into a surface having less deformation and smaller flatness.

Therefore, the non-magnetic ceramics for a recording / reproducing head of the present invention has a large Young's modulus with respect to alumina.
By uniformly dispersing titanium oxide, which has excellent sliding properties, the Young's modulus of the material itself can be improved, and it is possible to suppress deformation during grinding processing by a diamond grindstone, etc. It is possible to reduce the load during processing, increase the processing speed by ion milling, reduce the unevenness after processing, and reduce the frictional force and adsorption force with the disk.

By adding zirconia to the main component composed of titanium oxide and alumina, it is possible to improve chipping characteristics during machining and improve surface roughness after machining.

Further, the raw material particle size of titanium oxide is 0.6 μm.
By setting the particle diameter to m or less (50% particle size by Microtrac), the temperature range during pre-baking before hot pressing or HIP treatment can be set to a wide range of 1175 to 1300 ° C. and 95% or more. A pre-sintered body having a relative density is obtained, which enables subsequent HIP treatment. Moreover, by using such a titanium oxide having a raw material particle size of 0.6 μm or less, a composite material having a fine crystal particle size of the sintered body having an average crystal particle size of 1.0 μm or less can be produced. Titanium oxide raw material particle size is 0.6 μm
In the above, the range of the pre-baking temperature is limited, and the relative density is 95%.
This is because it becomes difficult to obtain the above stable pre-sintered body. As the pre-baking temperature increases, the particle size of titanium oxide crystals increases, and when the temperature exceeds 1300 ° C., titanium oxide and alumina react to synthesize aluminum titanate,
Since the hardness and Young's modulus decrease, it is necessary that aluminum titanate is not detected by X-ray diffraction measurement. In addition, the pre-firing temperature is high, or the raw material particle size is large, and the average crystal grain size of titanium oxide in the sintered body is 1 μm.
The material having a thickness of m or more was not suitable as a slider material because the surface roughness Ra of the processing surface finely processed by ion milling was as large as 100 nm or more.

Further, in order to enhance the insulating property of the slider, hot isostatic pressing (HIP) is performed in an argon atmosphere.
However, the volume resistivity of the material produced by the carbon hot pressing is as low as 10 ⁴ Ωcm. Further, when insulation is required, hot press treatment or HIP
By subjecting the treated material to a heat treatment in an oxidizing atmosphere, the volume resistivity can be made 10 ¹⁰ Ωcm or more.

[0026]

【Example】

Example 1 A raw material having an average particle size of 0.6 μm as titanium oxide and a raw material having an average particle size of 0.44 μm as alumina were weighed so that the composition of the sintered body was as shown in Table 1, and pulverized and mixed with alumina balls as a medium. The mixed raw materials are dried, passed through a 40 mesh and sized, then filled in a carbon mold and 350 kgf / cm.
A pressing force of ² was applied and hot pressing was performed at a temperature of 1150 ° C to 1300 ° C. The characteristics of the sintered body are shown in Table 1.

[0027]

[Table 1]

Here, the density was measured by using the Archimedes method, and the hardness was measured by using a hardness meter of AVK (manufactured by Akashi Seisakusho Co., Ltd.). The measurement condition is a load of 20 kgf with a Vickers indenter.
Was added for 15 seconds, and then the size of the indentation by the indenter was measured. A test piece having a cross section of 3 mm x 4 mm was prepared, and the strength was measured by a 3-point bending test method with a span of 30 mm. The speed of the head at this time is 0.5 mm / mi
It was set to n. The Young's modulus was measured by the pulse echo method by preparing a sample having the same shape as the strength measurement. For the presence or absence of pores, after polishing using diamond abrasive grains of 1 μm, the polished surface was observed with a scanning electron microscope to observe the presence or absence of pores of 1 μm or more.

Next, the volume resistivity is 3 mm × 4 mm × 4
Apply silver paste to both ends of 0mm test piece and 4
It was measured by the terminal method. At the same time, 110 in an oxidizing atmosphere
The volume resistivity of the sample after heat treatment at a temperature of 0 ° C. for 2 hours was measured. Further, the sample before heat treatment was milled using an argon source of Kaufman type Miratron (manufactured by Commonwealth) to determine the milling speed and milling surface roughness. The acceleration voltage was 800 V, and the argon beam was irradiated from an angle of 45 degrees with the normal to the processed surface of the sample.
For comparison, an alumina / titanium carbide composite material (TF700H) was simultaneously milled. For the surface roughness, a Nanoscope 2 atomic force microscope (AFM) manufactured by Digital Instruments was used. The AFM has a silicon nitride probe tip curvature R10n manufactured by Olympus Corporation.
A m-R30 nm probe was used.

The measurement visual field was 10 μm square.
The milling speed was measured by measuring the step difference between the milled surface and the covered surface using a surface roughness meter.

From Table 1, the non-magnetic ceramic of the present invention has a Young's modulus of 380 GPa or more, there is no pore of 1 μm or more in the sintered body, and the milling speed is 100.
It can be seen that the milling surface roughness is A / min or more and the milling surface roughness is also good. On the other hand, in the conventional alumina / titanium carbide composite material, although the Young's modulus is as high as 398 GPa, the load during processing is large, the milling speed is slow, and the milling surface roughness Ra is large.

Next, 1.6 × 2.2 × was applied to the sample before heat treatment.
A slider having two rails with a size of 0.9 mm was manufactured, and a CSS tester manufactured by Haruna Communication Co., Ltd. was used.
A test was conducted to evaluate the number of CSSs, disk damage, and head damage. The test method is performed by sliding a slider on the disk, the maximum rotation speed of the disk is 3600 rpm, and 3600 rp from the time of stop.
The time when m was set to 5 seconds was held at 3600 rpm for 3 seconds, stopped after 5 seconds, and the stopped state was set to 5 seconds.
This operation was performed once for the CSS. As a result, the sample No.
In the No. 12 material, the number of CSS times is 30,000 times, which damages the disk and the head.
It was confirmed that the sample No. 11 showed excellent sliding characteristics without damage to the disk or head even when the number of CSS cycles was 40,000.

Example 2 A raw material having an average particle size of 0.55 μm as titanium oxide and a raw material having an average particle size of 0.44 μm as alumina were weighed so that the composition of the sintered body was as shown in Table 2, and pulverized using alumina balls as a medium. Mixed. The mixed raw materials were dried and passed through 40 mesh to be sized, and then paraffin wax was added as a binder for granulation. And after molding this, 1175 ℃
To 1300 ° C. Table 2 shows the relative density calculated from the specific gravity and composition of the pre-baked body.

[0034]

[Table 2]

These pre-sintered bodies were subjected to HIP treatment at 1200 to 1300 ° C. for 1 hour in an argon atmosphere, and the density, hardness, strength, Young's modulus, presence or absence of pores, milling speed, and milling surface roughness were the same as in Example 1. The degree and volume resistivity were measured and recorded in Table 2. As the volume resistivity, the value after HIP and after heat treatment at a temperature of 1100 ° C. for 2 hours in an oxidizing atmosphere as in Example 1 are shown. The relative densities of the samples 14 to 20 of the present invention after HIP were 99.5% or more, and they were dense sintered bodies. Further, when the sliding characteristics of the sample before the heat treatment were examined in the same manner as in Example 1, in the samples No. 14 to 20, the CSS count was 40,000.
It was confirmed that there was no damage to the disk or head even after repeated rotation, and that it showed excellent sliding characteristics.

Comparative Example A raw material having an average particle size of 1.5 μm as titanium oxide and a raw material having 0.44 μm as alumina were weighed so that the composition of the sintered body was as shown in Table 3, and pulverized and mixed using alumina balls as a medium. The mixed raw materials were dried and passed through 40 mesh to be sized, and then paraffin wax was added as a binder for granulation. After molding, in an oxidizing atmosphere, 1175-1
Pre-baking was performed at 350 ° C. for 2 hours. Table 3 shows the relative density calculated from the specific gravity and composition of the pre-baked body.

[0037]

[Table 3]

These pre-sintered bodies were HIP-treated for 1 hour at 1200-1350 ° C. in an argon atmosphere. However, a dense sintered body having a relative density of 99% or more could not be manufactured. From this, the average particle size of titanium oxide is 1.5
It can be seen that when the raw material of μm is used, a dense sintered body cannot be produced even by the HIP treatment.

[0039]

As described above in detail, in the non-magnetic ceramics for a recording / reproducing head of the present invention, the Young's modulus of the material itself can be increased, which causes less deformation during processing and flatness of the air bearing surface. Can be precisely controlled, fine processing is possible, high processing speed, small irregularities on the fine processed surface, small friction force and attraction force generated between the head and disk, and excellent in sliding characteristics are obtained. be able to. As a result, for example, it is possible to obtain a non-magnetic ceramic for a read / write head, which is optimal for a ceramic substrate for a thin film magnetic head, a slider for various magnetic heads, a spacer for a magnetic head, a guide for a magnetic tape, and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram in which a deformation amount of a work in a state where a load is applied to the work during mirror finishing is calculated by a finite element method.

Claims (4)

[Claims] 1. A non-magnetic ceramic for a recording / reproducing head, which comprises titanium oxide in an amount of 1 to 17% by volume and alumina in an amount of 99 to 83% by volume. 2. A main component comprising 1 to 17% by volume of titanium oxide and 99 to 83% by volume of alumina, and the main component 1
A non-magnetic ceramic for a recording / reproducing head, characterized by containing 0.1 to 5 parts by weight of zirconia with respect to 00 parts by weight. 3. A mixed powder containing 1 to 17% by volume of titanium oxide and 99 to 83% by volume of alumina having a raw material having an average particle size of 0.6 μm or less, a molded body of the mixed powder, or a mixture of the mixed powder. A method for producing a non-magnetic ceramic for a recording / reproducing head, which comprises subjecting a sintered body to hot pressing or hot isostatic pressing. 4. A mixed powder containing 1 to 17% by volume of titanium oxide and 99 to 83% by volume of alumina having a raw material having an average particle size of 0.6 μm or less, a compact of the mixed powder, or the mixed powder. After hot pressing or hot isostatic pressing of the sintered body, it is 800 to 1200 ° C. in an oxidizing atmosphere.
A method for producing a non-magnetic ceramic for a recording / reproducing head, which comprises heat-treating.